Patent GB-1321721-A (GB)
Title: Apparatus for controlling photocomposition
Inventor: ROSS A
IPC: G03F3/08
Filed: 1971-01-15
Abstract: 1321721 Photocomposition PRINTING DEVELOPMENTS Inc 15 Jan 1971 [15 Jan 1970] 2192/71 Heading H4F Relates to photocomposition apparatus in which the size and location of segments of a colour transparency 12, Fig. 1, or of a plurality of separate transparencies (e.g. 12a, 12b, 12c, Fig. 1A, mounted on a transparent copy board 12d) are controlled in the preparation of colour separation images with the result that the segments or separate transparencies are reproduced in a desired pattern. In Fig. 1 the transparency 12 is scanned by a flying spot scanner 10 under control of circuit 20 which is shown in Fig. 2 and comprises on a transparent drum 50 an opaque mask 52 having in distinct segmental areas colour selective masks or filters 54, 55, 56 which are identical in size and location with the desired size and location of the desired pattern of the three transparencies 12a, 12b, 12c (or three segments of one transparency) to be recorded by the glow lamps 40-43, Fig. 1 as colour separation images on photographic film. Instead of being colour selective the filters 54, 55, 56 may be amplitude selective i.e. have different transmissivities. The mask is photoelectrically scanned and the resulting red, blue and green signals derived from filters 54, 55 and 56 respectively are supplied to gates 78-83. The axial and circumferential movements of drum 50 are encoded 85 as x and y signals and fed to sweep generators 88 and 90, the resulting sweep signals from which are fed to gates 78-83 as shown via variable resistors 91-96 and summing amplifiers 98- 104, to the other inputs of which variable D.C. voltages from networks 106-110 are supplied. By varying the resistances 91-96, x and y sweep voltages having varying slopes will be generated by the amplifiers 98-104, thereby controlling the area scanned by the flying spot scanner 10 (Fig. 1), and by varying the magnitude and polarity of the D.C. signals supplied to the amplifiers the position of the scanning beam of the scanner 10 is controlled. In operation, if red filter 54 corresponds to the desired size and location on the recorded separation images of the transparency 12b (scanning in the separation printer 38, Fig. 1, is effected synchronously with the scanning of mask 52), then when gates 78 and 79 are enabled by the output of red photoelectric device 74 appropriate deflection signals are passed to the scanner 10 so that transparency 12b is analysed in such a manner that it is reproduced with the size and at the location of filter 54 in the colour separation images. When the opaque portions of mask 52 are scanned NOR gate 84 is rendered conductive and the scanner 10 is blanked. Instead of being opaque, the non-filter portions of mask 52 may be transparent, a logic system (Fig. 3, not shown) being included between the coupling links 115a-117b, Fig. 2. With this latter mask, lettering may be superimposed on top of the pictures reproduced in the colour separation images by means of a knockout mask systems, the lettering being recorded as opaque letters on the filters 54-56. Instead of scanning the mask 52 as described, flat-bed, reciprocating or CRT scanning may be utilized and the mask may be reflective instead of transmissive.